Apparatus and method for sealing anodized aluminum parts

ABSTRACT

An apparatus for sealing an anodized aluminum oxide film includes a container with an airtight cover. The container has a sidewall and a bottom. A level sensor and a pressure gauge are mounted to the sidewall interior. The level sensor sends an alarm signal to shut off the heater if a liquid level falls below a predetermined value. The pressure gauge monitors pressure within the container. A heater is mounted in the bottom. A method of sealing an anodized aluminum oxide film with a thick and nonporous boehmite layer includes filling the apparatus with a sealing solution to a predetermined level; immersing the parts into the sealing solution; sealing the container with the cover; and heating the apparatus achieve a pressure of about 10 psi or higher, while maintaining the sealing solution in a liquid phase around the parts.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of U.S. provisional application No. 63/370,246, filed Aug. 3, 2022, the contents of which are herein incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to sealing anodized aluminum parts and, more particularly, to an apparatus and method for sealing anodized aluminum parts. Aluminum anodizing film is porous and vulnerable, and thus is usually sealed before being put into use, so as to improve its corrosion resistance and weather resistance. Currently available post-treatment devices generate a thin boehmite layer outside of the aluminum anodizing film which is ineffective at protecting the aluminum anodizing film from aggressive environments, such as long saltwater rinse and extreme pH environments such as a pH of around 2-4 or a pH of around 10-12.

U.S. patent Ser. No. 10/214,827B2 is drawn to methods of preparing metals with partially microcrystalline anodic coatings using methods involving several steps, including a hydrothermal sealing process in some cases. Example 10 illustrates a method including: immersing an anodized sample into metal salt solution for 10-30 minutes at about 85-95° F.; treating the substrate in NaOH solution for 3-5 minutes; immersing the substrate into a metal acetate solution for 20-45 minutes at about 185-195° F.; and subjecting the substrate to pressurized steam in a high-temperature, high-pressure chamber for 20 minutes to 5 hours at about 120° C.-150° C. and an autogenous pressure of 15 psi-70 psi. The results were compared to anodized aluminum samples sealed using either ambient nickel fluoride at 25° C. for 10 minutes or nickel acetate solution at 90° C. for 20 minutes.

As can be seen, there is a need for a post treatment device that generates a thick and nonporous protective boehmite layer outside of the porous anodized aluminum oxide film.

SUMMARY OF THE INVENTION

In one aspect of the present invention, an apparatus operative to seal an anodized aluminum oxide film with a thick and nonporous boehmite layer comprises a container having a sidewall and a bottom, with a heater mounted in the bottom; a level sensor mounted to an interior of the sidewall, operative to send an alarm signal to shut off the heater if a liquid level falls below a predetermined value; and a pressure gauge mounted at an inner top of the sidewall, operative to monitor pressure within the container; and an airtight cover.

In another aspect of the present invention, a method of sealing an anodized aluminum oxide film with a thick and nonporous boehmite layer comprises filling the apparatus with a sealing solution to a predetermined level; immersing the anodized aluminum parts into the sealing solution; sealing the container with the cover; and heating the apparatus to a temperature associated with a pressure of about 10 psi or higher, maintaining the temperature and pressure for a period of time while maintaining the sealing solution in a liquid phase around the anodized aluminum parts.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an anodizing apparatus according to an embodiment of the present invention;

FIG. 2 is another schematic view thereof, shown filling with a sealing solution;

FIG. 3 is another schematic view thereof, shown in use;

FIG. 4 is another schematic view thereof, shown in use;

FIG. 5 is another schematic view thereof;

FIG. 6 is another schematic view thereof; and

FIG. 7 is a flow chart of a method of sealing anodized aluminum according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description is of the best currently contemplated modes of carrying out exemplary embodiments of the invention. The description is not to be taken in a limiting sense but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.

Broadly, one embodiment of the present invention is a post-sealing method of anodized aluminum parts and a covered container apparatus therefor.

Utilizing the inventive method, the anodized aluminum oxide film achieves much stronger chemical/corrosion resistance. After treatment, the anodized aluminum oxide film may withstand aggressive environments, such as a long saltwater rinse, a high pH environment of about 10-12, and a low pH environment, i.e., about 2-4.

The container and cover may be made of a heavy-duty material, such as stainless steel. The cover may comprise a rubber gasket, locking in an airtight seal when the cover is closed over the container. The shape of the container is not particularly limited and may be round or square, for example.

The container may be filled with an aqueous nickel sealing solution or water to a predetermined level. In some embodiments, the sealing solution/water may be added to the container manually. In other embodiments, the container may be filled automatically by a level sensor and controller, via an inlet pipe and pump.

A controller with pre-programmed microchips may be mounted on the outside wall of the container. The controller may control a heater, a level sensor, and a pressure gauge, making it easy to operate steam pressure, seal solution level and heat by adjusting settings.

The controller may have a timer setting as well as a cycle setting that may be adjusted. When the preset pressure is reached, the timer counts down to a preset time. Once the time or cycle is completed, the controller may automatically shut off the heater. The sealing process is completed and the user may remove the parts.

The sealing solution may be heated with a heater at the bottom of the container. The heater may have at least two settings set at the controller: a high heat setting and a low heat setting. The high heat setting may be activated at the beginning of the process. After a preset steam pressure is reached, the controller may automatically change to the low heat setting, switching back to the high heat setting if the steam pressure falls below a preset value. The temperature inside the container may reach about 110° C. or higher, such as up to about 140° C.

The sealing solution/water level inside the container may be monitored with a level sensor mounted to the container inner sidewall. If the level falls below a predetermined value during the process, the level sensor may send an alarm signal to the controller to shut off the heater for safety.

The steam pressure during the sealing run may be controlled via a pressure gauge mounted at the top of the container inner sidewall. The controller may be set at a pressure of about 10 psi or higher, such as up to about 25 psi, monitored by the pressure gauge. Once the steam pressure inside the container reaches the preset pressure, a release valve on the cover may open to release excess steam, maintaining the high temperatures within the container at a constant level.

In some embodiments, depending on the shape of the parts, a rack may be used to hold the anodized aluminum parts (whether soft film or hard film). The parts are fixed to the rack. The rack is clipped on a removable rack hanger. The rack hanger ends may be clipped on the wall inside the container above the sealing solution, suspending the rack and attached parts in the solution.

The apparatus of the invention may be operated by the following method. The apparatus may be plugged in a power supply. The user may open the cover and fill the container with sealing solution or water to a predetermined level indicated by the level sensor. The user may hang parts on the rack and mount the rack to the rack hanger. The rack hanger may be hung on the container with the parts immersed in the sealing solution or water. The user may close the cover, checking to make sure it is well sealed on the container. Using settings on the controller, the user may set the pressure and turn on the heater. The steam inside the container may reach the preset pressure after about 10-20 minutes. Once the pressure gauge indicates that the preset pressure has been achieved, the user may start a timer for the sealing treatment. After a predetermined time, such as about 1 hour or more, e.g., up to about 2 hours, the user may shut down the heater and the sealing process is completed. After waiting about 5-10 minutes or until the steam pressure as indicated by the pressure gauge reaches 1 atmosphere, the user may open the cover and remove the rack with parts.

Referring now to FIGS. 1 through 7 , FIG. 1 illustrates a sealing apparatus container 18 according to an embodiment of the present invention. A pressure gauge 22 and a level sensor 26 mounted on an inner sidewall of the container 18 and a heater 28 embedded in a base of the container 18 electronically communicate with a controller 24.

As shown in FIG. 2 , the container 18 may be filled with sealing solution prior to use.

Parts 16 may be suspended in the container 18 on a rack 14 from a rack hanger 12, as seen in FIG. 3 .

Once the rack hanger 12 is installed on the container 18 sidewall, the container 18 may be sealed by installing a cover 10; see FIG. 4 . The container 18 may be operated according to method steps disclosed in FIG. 7 .

As illustrated in FIG. 5 , once the sealing process is completed, the cover 10 may be removed from the container 18 and, as shown in FIG. 6 , the hanger 12 may be removed, removing the rack 14 and parts 16 from the solution 20.

A method of operating the sealing apparatus is shown in FIG. 7 . Once the unit 18 is connected to a power supply and the cover 10 is in an open position, the user may fill the unit 18 with water or a sealing solution 20 to a level adequate to immerse parts to be sealed. The level is monitored using the leveling sensor 26. The aluminum parts 16 may be loaded onto a rack 14 and the rack may be loaded onto a rack hanger 12, which is lowered into the container 18 until the parts 16 are fully immersed in the water or sealing solution 20. The user may close the cover 10 to establish an airproof seal, set a selected pressure using a pressure gauge 22, and turn on the heater 28. Once a preset pressure is achieved, the user may start a timer on the controller 24. Alternatively, the timer may automatically initiate once the controller 24 determines the pressure has been achieved. After one to two hours, the heater 28 may be shut off. Waiting until the pressure reaches 1 atm (atmospheric pressure), approximately 10-20 minutes, the user may open the cover 10 and remove the rack 14 with the parts 16.

Examples

Six 3″×4″×0.1″ aluminum panels (total exposed test area of 150 in²), anodized with a 1 mil-thick type III hard coating, were treated in an apparatus according to an embodiment of the present invention in DI water at 15 psi and 125° C. for 1 hour. The six panels were subjected to a salt spray corrosion test conducted according to ASTM B117-19 for 1000 hours at an incline of 6° from vertical. The conditions were as follows.

Type of Salt and Water Morton ® Culinox ® 999/DI Type IV Exposure Zone Temperature 95° F. Average Volume of Salt Solution per 1.5 ml/hr. 80 cm² Average Specific Gravity/Temp 1.033 @ 23° C. Average Concentration of Salt Solution 5% Average pH of Salt Solution 6.7 Method of Cleaning Prior DI Wash/Dried with cloth Method of Cleaning Post Salt Spray Water Rinse/Dry Method of Support Plastic Rack Method of Protection (Cut Edges, ID Top Edge Protected w/Tape Marks, Rack) Interruptions in exposure None/Continuous Operation

The industrial specification MIL-PRF-8625F requires that test specimens having an exposed surface area of 30 in² with a hard coating exhibit no more than five isolated spots or pits after 336 hours and that none of the spots or pits is larger than 0.031″ in diameter. All six panels exhibited no pitting after 1000 hours.

It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims. 

What is claimed is:
 1. An apparatus operative to seal an anodized aluminum oxide film with a thick and nonporous boehmite layer, comprising: (a) a container having a sidewall and a bottom, with (i) a heater mounted in the bottom; (ii) a level sensor mounted to an interior of the sidewall, operative to send an alarm signal to shut off the heater if a liquid level falls below a predetermined value; and (iii) a pressure gauge mounted at an inner top of the sidewall, operative to monitor pressure within the container; and (b) an airtight cover.
 2. The apparatus of claim 1, further comprising a controller having an adjustable timer setting and an adjustable cycle setting, mounted on an outside surface of the sidewall, wherein the controller is operative to control the heater.
 3. The apparatus of claim 1, further comprising a removable rack operative to suspend anodized aluminum parts within the container mounted to the interior of the sidewall.
 4. The apparatus of claim 1, wherein the container and the airtight cover are formed of stainless steel.
 5. A method of sealing an anodized aluminum oxide film with a thick and nonporous boehmite layer, comprising: (a) providing the apparatus of claim 1; (b) filling the apparatus with a sealing solution to a predetermined level; (c) immersing the anodized aluminum parts into the sealing solution; (d) sealing the container with the airtight cover; and (e) heating the apparatus to a temperature associated with a pressure of at least about 10 psi; maintaining the temperature and pressure for a period of time while maintaining the sealing solution in a liquid phase around the anodized aluminum parts.
 6. The method of claim 5, wherein the sealing solution is an aqueous nickel solution or water.
 7. The method of claim 5, returning the interior of the container to about 1 atmosphere pressure and removing the anodized aluminum parts.
 8. The method of claim 5, wherein the heater maintains a temperature inside the container of at least about 110° C.
 9. The method of claim 5, wherein the period of time is about 1 to about 2 hours.
 10. The method of claim 5, wherein the period of time comprises a first period of time with the heater at a first heat setting until a preset steam pressure is reached; and second period of time with the heater at a second heat setting lower than the first heat setting.
 11. The method of claim 10, wherein if the pressure falls below the preset steam pressure, operating the heater at the first heat setting to recover the preset steam pressure. 